The invention relates to folding ladders of the kind comprising a series of modules, each module including a pair of spaced, parallel stile sections connected together by a transverse tread section, the modules being of decreasing size and each module, except for the largest one, being pivotally mounted between the stile sections of the adjacent larger module, so as to be foldable between an extended position and a folded position in which the smaller module is nested within the larger module, releasable locking means being provided to lock each module in the extended position.
This provides a ladder which, when folded, is very compact in shape since the modules nest one within another so that the overall size of the folded ladder is little greater than the size of the largest module.
While arrangements are known in which the tread sections are bolted to the stile sections, it has usually been considered necessary to connect the tread sections to the stile sections by welding in order to provide the necessary strength and rigidity which a ladder, and particularly a folding ladder, must have. Accordingly, existing folding ladders of this kind have usually been made of steel, in order to permit such welding. This has the disadvantage that manufacture of each module is time-consuming and requires operator skill, as well as the use of welding equipment. Also, since the sections are made of steel, they are comparatively heavy and expensive to produce.
It is the object of the invention to provide a folding ladder which is strong and rigid, but which is light in weight and simple and inexpensive to manufacture.
According to the invention, a folding ladder of the kind first referred to is characterised in that the tread and stile sections are hollow, and in that the transverse tread section of each module is connected to each of its associated stile sections by a separately formed joint member, one end of which projects into the hollow stile section and is secured thereto, and the other end of which projects into the hollow tread section and is secured thereto.
Preferably, each hollow stile section is formed, in one side wall thereof, with an aperture so shaped that one end of the joint member projects through the aperture and into the interior of the stile section. The end of the joint member which projects into the interior of the hollow stile section may engage the side wall of the stile section which is opposite the aperture, and may be secured thereto by fasteners which pass through said opposite side wall and engage with the joint member.
Said other end of the joint member may project axially into the open end of the hollow tread section, and may be an interference fit thereon. It may be secured within the open end of the hollow tread section by fasteners which pass through a side wall of the tread section and engage with the joint member.
The releasable locking means associated with each module may include a bolt which is slideable within a passage in each joint member, the passage being in register with an aperture in the outwardly facing side wall of the stile section to which the joint member is secured so that the end of the bolt may project through said aperture, the inwardly facing side wall of the adjacent stile section on the adjacent larger module being formed with an aperture shaped and positioned to receive the projecting end of the bolt when the two modules are in the extended position, thereby to retain the modules in the extended position. Preferably, spring means are provided to urge the bolt normally into its projecting position. The spring means may, for example, comprise a helical compression spring encircling the bolt within the passage in the joint member and disposed between abutments on the bolt and joint member respectively.
Each bolt may be connected by a link to a manipulating member which is slideable in a slot in a side wall of the tread section, whereby the bolt may be retracted by sliding the manipulating member along the slot, each tread section being provided with two such bolts and manipulating members, and the manipulating members being located adjacent one another so that they may be operated simultaneously to retract both bolts.